Digital Commons Network^™

Active Minimization Of Acoustic Energy Density In A Mock Tractor Cab, Benjamin Mahonri Faber

Theses and Dissertations

An active noise control (ANC) system has been applied to the problem of attenuating low-frequency tonal noise inside small enclosures. The intended target application of the system was the reduction of the engine firing frequency inside heavy equipment cabins. The ANC system was based on a version of the filtered-x LMS adaptive algorithm, modified for the minimization of acoustic energy density (ED), rather than the more traditional minimization of squared acoustic pressure (SP). Three loudspeakers produced control signals within a mock cabin composed of a steel frame with plywood sides and a Plexiglas® front. An energy density sensor, capable of …

Examination Of Adolescent Physical Activity And Overweight Levels , Maika Elizabeth Nelson

Theses and Dissertations

Research suggests declines in physical activity may occur after age 12. The purpose of this study was to determine the relationships between adolescent physical activity, BMI, and nutrition. Adolescents, ages 12-17 (N = 223), wore pedometers for 11 consecutive days and completed a nutrition survey, the Youth Adolescent Questionnaire. Activity levels did not differ among the ages of 12-17 year old adolescents, and boys were more active than girls. There was a low, but significant relationship between BMI and physical activity levels for both boys and girls. Energy intake was not related to BMI or physical activity levels in boys …

A Forbidden Subgraph Characterization Problem And A Minimal-Element Subset Of Universal Graph Classes, Michael D. Barrus

Theses and Dissertations

The direct sum of a finite number of graph classes H_1, ..., H_k is defined as the set of all graphs formed by taking the union of graphs from each of the H_i. The join of these graph classes is similarly defined as the set of all graphs formed by taking the join of graphs from each of the H_i. In this paper we show that if each H_i has a forbidden subgraph characterization then the direct sum and join of these H_i also have forbidden subgraph characterizations. We provide various results which in many cases allow us to exactly …

Using Graphics, Animations, And Data-Driven Animations To Teach The Principles Of Simple Linear Regression To Graduate Students, Daniel Taylor Rowe

Theses and Dissertations

This report describes the design, development, and evaluation of the Simple Linear Regression Lesson (SLRL), a web-based lesson that uses visual strategies to teach graduate students the principles of simple linear regression. The report includes a literature review on the use of graphics, animations, and data-driven animations in statistics pedagogy and instruction in general. The literature review also summarizes the pertinent instructional design and development theories that informed the creation of the lesson. Following the literature review is a description the SLRL and the methodologies used to develop it. The evaluation section of the report details the methods used during …

An Analysis Of Factors That Have Influenced The Evolution Of Information Assurance From World War I Through Vietnam To The Present, Kelvin B. Scott

Theses and Dissertations

This study is an exploratory historical analysis of the factors that have influenced the evolution of military Information Assurance (IA) programs from World War I to the present. Although the term IA has recently been widely used throughout the Information Resource Management field (IRM), evidence indicates that information and information systems protection mechanisms were used during every U.S. Military conflict. This research proposes to increase the body of knowledge within the information systems management field by exploring the areas related to Information Assurance (IA) and the ultimate goal of U. S. Defensive Information Warfare. I found that significant events related …

Analysis And Design Of Low-Jitter Oscillators, Justin Jennings Fitzpatrick

Theses and Dissertations

This thesis presents an examination of the jitter performance of different oscillator types in the presence of flicker noise, white noise and power supply noise. Key results are achieved using time domain simulations to determine cycle jitter of several different oscillator architectures, semiconductor processes and component features. In the end, a design procedure is developed for creating a low-jitter oscillator in a TSMC .25mm CMOS semiconductor process.

Problems Related To The Zermelo And Extended Zermelo Model, Benjamin Zachary Webb

Theses and Dissertations

In this thesis we consider a few results related to the Zermelo and Extended Zermelo Model as well as outline some partial results and open problems related thereto. First we will analyze a discrete dynamical system considering under what conditions the convergence of this dynamical system predicts the outcome of the Extended Zermelo Model. In the following chapter we will focus on the Zermelo Model by giving a method for simplifying the derivation of Zermelo ratings for tournaments in terms of specific types of strongly connected components. Following this, the idea of stability of a tournament will be discussed and …

An Exploratory Study Of The Effectiveness Of The Cpj In Defending Journalists And Press Freedom Ideals In Latin America: Transnational Advocacy In The International Sphere, Leticia A. Adams

Theses and Dissertations

The Committee to Protect Journalists (CPJ) is one of many nonprofit, nongovernmental organizations that work to defend press freedom and the safety of journalists in Latin America. Based on qualitative interviews with employees at the CPJ, open surveys with journalists who have been helped by the CPJ, historical archive research, and informal participant observation, this study shows that organized domestic and international nongovernmental groups can and do make improvements on behalf of journalists and press freedom in Latin America. The CPJ's activities raise issues and place them on the agenda, and they influence discourse, policy, institutional procedures, and state behavior. …

Full-Scale Lateral-Load Tests Of A 3x5 Pile Group In Soft Clays And Silts, Jeffrey L. Snyder

Theses and Dissertations

A series of static lateral load tests were conducted on a group of fifteen piles arranged in a 3x5 pattern. The piles were placed at a center-to-center spacing of 3.92 pile diameters. A single isolated pile was also tested for comparison to the group response. The subsurface profile consisted of cohesive layers of soft to medium consistency underlain by interbedded layers of sands and fine-grained soils. The piles were instrumented to measure pile-head deflection, rotation, and load, as well as strain versus pile depth.

Phylogenetic Systematics And Evolution Within The Family Scincidae, Alison Swindle Whiting

Theses and Dissertations

Scincidae (skinks) comprise one of the largest families of lizards, and the more than 1300 species show great variation in body size and form, and are found worldwide in a diversity of habitats. The group presents many interesting questions ranging from the colonization of oceanic islands, to the evolution of limb loss, yet most of these and other questions remain understudied. The purpose of this dissertation is to use multiple mitochonidrial and nuclear DNA markers in connection with current cladistic methods to address evolutionary questions at many levels within Scincidae. In chapter one, a molecular phylogenetic study, based on six …

Perspectives Of Pro-Revivalism: The Christian History And The Great Awakening, Lisa Thurston Brown

Theses and Dissertations

The Christian History was a pro-revivalist magazine printed in Boston from 1743-1745 during what is known as the Great Awakening. It contained accounts of revivalism written by pro-revivalist ministers from throughout the American colonies, England and Scotland. These ministers believed that the Holy Spirit was being poured out upon the land in a shower of grace, causing unprecedented numbers of people to convert to Christ. In The Christian History, pro-revivalist ministers expressed their support for the revivals and shared their experiences. Thus the magazine has typically been viewed as religious propaganda advocating a single, polemical viewpoint. However, in spite …

Autonomous Landing Of A Rotary Unmanned Aerial Vehicle In A Non-Cooperative Environment Using Machine Vision, Joshua Martin Hintze

Theses and Dissertations

Landing an Unmanned Aerial Vehicle (UAV) is a non-trivial problem. Removing the ability to cooperate with the landing site further increases the complexity. This thesis develops a multi-stage process that allows a UAV to locate the safest landing site, and then land without a georeference. Machine vision is the vehicle sensor used to locate potential landing hazards and generate an estimated UAV position. A description of the algorithms, along with validation results, are presented. The thesis shows that software-simulated landing performs adequately, and that future hardware integration looks promising.

Design Of A High Speed Mixed Signal Cmos Mutliplying Circuit, David Ray Bartholomew

Theses and Dissertations

This thesis presents the design of a mixed-signal CMOS multiplier implemented with short-channel PMOS transistors. The multiplier presented here forms the product of a differential input voltage and a five-bit digital code. A TSMC 0.18 µm MOSFET model is used to simulate the circuit in Cadence Design Systems. The research presented in this thesis reveals a configuration that allows the multiplier to run at a speed of 8.2 GHz with end-point nonlinearity less than 5%. The high speed and low nonlinearity make this circuit ideal for applications such as filtering and digital to analog conversion.

Simulating A Chromotomographic Sensor For Hyperspectral Imaging In The Infrared, Anthony J. Dearinger

Theses and Dissertations

Hyperspectral imaging systems passively sense radiant electromagnetic energy from a remote scene to form a three dimension profile of the remote scene. The data contained in this profile describes real images of the remote scene for a certain number of spectral wavelength bands across a finite spectral range of electromagnetic radiation. Typical grating type hyperspectral imaging systems collect spectral electromagnetic radiation in the visible and near infrared spectral range, by incrementally scanning across the spatial extent of the remote scene. The legacy of low optical throughput because of the optical scanning techniques employed in these systems means adapting these systems …

Cross-Sectional Study On The Factors That Influence E-Learning Course Completion Rates, Christopher C. Earnhardt

Theses and Dissertations

Completion rates for web-based courses tend to lag behind their traditional classroom counterparts, sometimes as much as 40% (Carter, 1996; Phipps and Merisotis, 1999; Zielinski, 2000). Thurston and Reynolds (2002) employed motivational constructs to explain why some people persist while others drop out of web-based courses. Their analysis of 8 web-based courses and response from 497 active duty Air Force students indicated that completion goals, off-task distractions, availability of feedback for self-regulation, and continued confidence were important factors that distinguished those who completed their courses from those who did not. This study addresses the limitations of the previous study and …

Group Performance In Military Scenarios Under Deceptive Conditions, Michael C. Hass

Theses and Dissertations

The goal of this research was to investigate how changes in modality (communication type) and external conditioning (warnings of player deception) relate to perceptions of deception and task difficulty and in turn how these perceptions relate to the final group game scores in a cooperative effort with conflicting goals. One hundred and eight participants were grouped into teams of three, given similar instructions but different goals, and asked to play a cooperative game called StrikeCOM that mimics the intelligence gathering needed to develop an air tasking order and subsequent air strike on three military targets. The analysis of the post-game …

An Experimental Design For Measuring In Situ Radiation Damage To A Piezoelectric Transducer, Michael R. Severson

Theses and Dissertations

An experiment was conducted investigating the use of an acoustic pulse waveguide to collect response measurements from three piezoelectric acoustic emission (AE) transducers while the transducers were exposed to an active nuclear reactor neutron flux ranging from 1 x 10¹¹ to 2.4 x 10¹² neutrons per cm². Material, mechanical, and radiation studies were performed to determine a practical design for the construction of the experiment. Discreet frequency pulses generated by an Arbitrary Waveform Generator were transmitted by an aluminum waveguide to the core of the Ohio State University Research Reactor (OSURR). Three AF transducers coupled to …

An Analysis Of Electromagnetic Interference (Emi) Of Ultra Wideband(Uwb) And Ieee 802.11a Wireless Local Area Network (Wlan) Employing Orthogonal Frequency Division Multiplexing (Ofdm), Juan Lopez Jr.

Theses and Dissertations

Military communications require the rapid deployment of mobile, high-bandwidth systems. These systems must provide anytime, anywhere capabilities with minimal interference to existing military, private, and commercial communications. Ultra Wideband (UWB) technology is being advanced as the next generation radio technology and has the potential to revolutionize indoor wireless communications. The ability of UWB to mitigate multipath fading, provide high-throughput data rates (e.g., greater than 100 Mbps), provide excellent signal penetration (e.g., through walls), and low implementation costs makes it an ideal technology for a wide range of private and public sector applications. Preliminary UWB studies conducted by The Institute for …

Implementation Issues Of Real-Time Trajectory Generation On Small Uavs, Derek B. Kingston

Theses and Dissertations

The transition from a mathematical algorithm to a physical hardware implementation is non-trivial. This thesis discusses the issues involved in the transition from the theory of real-time trajectory generation all the way through a hardware experiment. Documentation of the validation process as well as modifications to the existing theory as a result of hardware testing are treated at length. The results of hardware experimentation show that trajectory generation can be done in real-time in a manner facilitating coordination of multiple small UAVs.

Measuring Small Business Participation In Air Force Contracting: The Impact Of Acquisition Reform, William C. Pike

Theses and Dissertations

Congress has mandated the Air Force to reform and streamline its acquisition procedures while promoting participation by small business contractors. Reports on the federal government as a whole suggest that the acquisition reforms have had a negative effect on small business participation, with a declining number of small businesses receiving contract awards. A causal regression model is used to determine that the Air Force has actually increased the number of small businesses receiving contract awards over the past thirteen years and has maintained a steady stream of new small businesses into that group. Variables are tested to determine their effect …

Influence Of Consolidation And Interweaving On Compression Behavior Of Isotruss™ Structures, Steven Matthew Hansen

Theses and Dissertations

Composite IsoTruss™ structures incorporate intersecting longitudinal and helical members. At the intersections, the fiber tows can be interwoven to achieve mechanical interlocking for increased joint integrity. Interlocking introduces gaps and curvilinear fiber paths similar to the crossovers in filament-wound structures, potentially facilitating local delamination within the members, thus reducing the strength and/or damage tolerance of the structure. Optimizing the interlocking pattern at the joints along with efficient consolidation minimizes these effects.

Joint specimens were fabricated using a specially designed machine. Specific tow intersection patterns at the joint were: 1) Completely encapsulating the longitudinal member with the tows of the helical …

Percolation Paths Of Three-Dimensions In Sensitized Stainless Steel, Alisa Jean Henrie

Theses and Dissertations

The study of three-dimensional percolation paths through materials is important in its contribution to understanding defect sensitive properties of materials. This work shows the importance of grain boundary character in modeling defect sensitive boundaries. Also presented are trends of percolation of sensitized grain boundaries in 304 stainless steel (304SS). Of particular interest is how open paths form in a three-dimensional model created through serial sectioning. Evidence is presented that triple or quadruple points that contain typically two boundaries with special character that intersect the percolation path break up the path. Some grains with no known special qualities (i.e., CSL) have …

Characterization Of Ultra Wideband Multiple Access Performance Using Time Hopped-Biorthogonal Pulse Position Modulation, Donald J. Clabaugh

Theses and Dissertations

The FCC's release of its UWB First Report and Order in April 2002 spawned renewed interest in impulse signaling research. This work combines Time Hopped (TH) multiple access coding with 4-ary UWB Biorthogonal Pulse Position Modulation (TH-BPPM). Multiple access performance is evaluated in a multipath environment for both synchronous and asynchronous networks. Fast time hopping is implemented by replicating and hopping each TH-BPPM symbol NH times. Bit error expressions are derived for biorthogonal TH-BPPM signaling and results compared with previous orthogonal TH-PPM work. Without fast time hopping (NH = 1), the biorthogonal TH-BPPM technique provided gains equivalent to Gray-coded QPSK; …

An Investigation Of The Role Of Influence Behaviors In Information System Implementation: A Case Study Of The Air Force Institute Of Technology School Of Engineering And Management Student Academic Support System, Mary M. King

Theses and Dissertations

Organizations implement information systems (IS) for various reasons such as streamlining daily functions and keeping pace with changes in technology. Influence behaviors demonstrated by key leaders in reference to the implementation of such information systems play a key role in their acceptance and success. This research looks at a specific case of IS implementation and the role influence behaviors played in the successfulness of the system. This research is a case study of the Air Force Institute of Technology's (AFIT) implementation of an academic support system called my.afit.edu. Interviews and documentation gathered from key parties involved in the implementation provided …

Verification Of Meteorological Data Reports From The Rq-4a Global Hawk Unmanned Aerial Vehicle, Steven M. Callis

Theses and Dissertations

Unmanned aerial vehicles (UAVs) have onboard sensors that continuously record weather data during their missions. This information is extremely valuable to both the meteorological and UAV communities with numerous potential benefits, which include improved weather forecast products and additional weather intelligence for military planners. The value of any dataset is directly related to its accuracy and this research determined the accuracy of weather data obtained from a particular UAV, the RQ-4A Global Hawk. This was accomplished through statistical analysis and comparisons with upper-air data and Atmospheric Slant Path Analysis Model (ASPAM) profiles of the atmosphere. Recommendations are provided for the …

An Experimental Investigation Of Productivity Stratification And Knowledge Transfer In An Electronically Mediated Environment, Jachin Sakamoto

Theses and Dissertations

The idea of anywhere and anytime learning is enticing from a military standpoint, given the high deployment rates in the current operational environment. Electronic-based learning is seen as an answer to this requirement. Currently there are many variations in electronic-based instructional media, and little has been done to determine which format or combination of formats is most conducive to facilitating knowledge transfer and learning. The research project explores, through the use of an experiment, three primary constructs of media richness, content flexibility, and forced engagement, in their relation to effectiveness or productivity in facilitating learning in the experimental participants. The …

Lattices And Their Applications To Rational Elliptic Surfaces, Gretchen Rimmasch

Theses and Dissertations

This thesis discusses some of the invariants of rational elliptic surfaces, namely the Mordell-Weil Group, Mordell-Weil Lattice, and another lattice which will be called the Shioda Lattice. It will begin with a brief overview of rational elliptic surfaces, followed by a discussion of lattices, root systems and Dynkin diagrams. Known results of several authors will then be applied to determine the groups and lattices associated with a given rational elliptic surface, along with a discussion of the uses of these groups and lattices in classifying surfaces.

Beamforming Techniques And Interference Mitigation Using A Multiple Feed Array For Radio Astronomy, Chad K. Hansen

Theses and Dissertations

Radio frequency interference has become a large problem to radio astronomers. This thesis proposes the idea that radio frequency interference can be mitigated using a phased array feed in conjunction with a large reflector. A phased array feed would allow radio astronomers to observe fainter signals than is currently possible, while at the same time enabling rapid sky surveys. A phased array feed was designed and simulated, and sensitivity optimization was performed on the array feed. It was shown that higher sensitivity can be achieved using a 7-element phased array feed than with a conventional waveguide feed. Simulations were ran …

Magnetogasdynamic Flow Control Of A Mach Reflection, Brian E. Earp

Theses and Dissertations

Two-dimensional regular and Mach reflections have been studied in the Mach 4.96 dual-solution domain for a 25° and 26° double-fin inlet. The steady-state computational Mach and regular reflections were subjected to magnetogasdynamic forces to determine whether these forces could be used as a possible flow control mechanism. The numerical code employed for this research solved the inviscid Euler equations with added source terms for the ponderomotive force and accompanying energy interactions. The 25° regular reflection was determined to be extremely sensitive to a decelerating Lorentz force. Transient application of the force led to the transition of the regular reflection to …

Establishing A Foundation To Capture The Cost Of Oversight For A Major Defense Program Within The Information Technology (It) Acquisition Community, Monroe Neal Jr.

Theses and Dissertations

In 1970 the Department of Defense introduced the Department of Defense Directive 5000 (DoD 5000) to standardize the acquisition process. The directive created oversight forums to ensure the policies and procedures created were followed, to track program progress, and to identify programs in trouble. Although oversight was essentially created to help reduce the cost of acquisitions, there is reason to believe that it may increase the costs. However, because only been a few studies have been conducted to estimate the cost of oversight, no one knows how much "oversight" actually costs individual programs. Numerous oversight processes are being used today, …